1. Field of the Invention
The present invention relates to a micro contact element (probe) used as a connecting medium between a test apparatus and a device under test, a base member for mounting of the micro contact element and a micro contact device (probe card) comprising the micro contact element and the base member, and more particularly to such a micro contact element that is insertable into the base member when assembling to form the micro contact device. The present relates also to methods of making respectively the micro contact element and the base member for the micro contact element.
2. Description of the Related Art
When testing high-density or high-speed electrical devices (for example, LSI or VLSI circuits), a probe card having a big amount of micro contact elements (probes) shall be used. By means of the flexible and electrically conductive property of the micro contact elements, the probe card is used as an electric connection medium between the test apparatus and the device under test, for example, an LSI chip, VLSI chip, semiconductor wafer, semiconductor chip, semiconductor package, printed circuit board, or LCD panel. Micro contact elements can also be used as lead wire means for an IC package. For easy understanding of the present invention, the micro contact elements described hereinafter can be treated, but not limited to, as probes for probe cards.
U.S. Pat. No. 6,268,015 discloses a method of forming an interconnection, including a spring contact element, by lithographic techniques. A spring contact element made according to this method, as shown in FIG. 1, includes a post portion 3, a beam portion 2, and a tip structure portion 1. This method requires several assembly procedures to bonding the post portion 3, beam portion 2 and the tip structure portion 1 in position together after formation of the aforesaid elements by respective metal-depositing processes, easily resulting in improper positioning of the tip structure portion and low uniformity of the spring contact elements of the probe card.
According to U.S. patent publication serial No. 20010012739, the contact element is made by metal deposition by means of micro electromechanical techniques. However, the point (tip structure) is bonded to the beam by welding, and the post (contact element base) is made by wire bonding with the outside wall electroplated with a metal coating. The wire bonding process for making the post is complicated and requires much manufacturing time. Further, this method requires high precision control techniques.
U.S. Pat. No. 6,399,900 discloses a contact structure for achieving an electrical connection with a contact target, which is formed by producing a contactor on a planar surface of a substrate by microfabrication technology. The tip of the contactor is also bonded to an end of the beam by welding and the beam has the other end thereof merely attached to the planner surface of the substrate via the adhesion between metal and substrate, thereby lowering the stability of the contactor. The contactor might detach from the planner surface of the substrate due to fatigue under long-lasting and repeated operation. Furthermore, if the positioning of the tip bonded to the beam by welding is inaccurate due to inaccuracy welding process, the uniformity of contact force applied on each tip will deteriorate so as to degrade the quality of probing and testing accuracy.
Further, U.S. Pat. No. 5,974,662 discloses a probe card assembly, which includes a probe card, a space transformer having resilient contact structures (probe elements) mounted directly to and extending from terminals on a surface thereof, and an interposer disposed between the space transformer and the probe card. The space transformer and interposer are “stacked up” so that the orientation of the space transformer, hence the co-planarity of the tips of the probe elements, can be adjusted without changing the orientation of the probe card. However, this design has a complicated structure, and the long transmission path is not suitable for high frequency transmission.